Lead in the environment presents a significant health risk, especially to children. Lead-based paint from older buildings has been one of the primary sources of lead-caused morbidity. The ability of microorganisms to bioaccumulate or to remove heavy metals from aqueous systems has been noted. Applications have included removal of metals from sewage or industrial effluent and mining of precious heavy metals, and for recovering polluting metals from geothermal ponds. However, lead removal from soil can be more difficult due to the chemistry of binding mechanisms in the soil.
Vesper, et al, ("Microbial Removal of Lead from Solid Media and Soil". Water, Air, & Soil Pollution. 86:207-219 (1996) reported use of a strain of Pseudomonas aeruginosa (the organism used in the instant application) to remove lead from solidified media and soil. However, they did not report use of the organism in the presence of phosphate to provide an insoluble form of lead, but only reported that the organism could sequester lead. There is no suggestion therein that the organisms could sequester other heavy metals.
Ryan, et al, in U.S. Pat. No. 5,512,702, teaches that addition of calcium phosphate to lead-containing soil resulted in formation of insoluble lead phosphate. However, no use of any microorganisms is reported or suggested therein. Furthermore, the calcium phosphate required therein, while appropriate for use in soil, would not necessarily be appropriate for use in other ecosystems or in solutions containing lead or other heavy metals. Significant theoretical and experimental evidence supports the hypothesis that lead phosphates are the most insoluble and stable forms of Pb in soils. Among all the Pb-P minerals, chloropyromorphite has one of the lowest solubilities; thus it is one of the most stable under favorable environmental conditions (Nriagu, J. O., "Lead Orthophosphates-II. Stability of Chloropyromorphite at 25.degree. C." Geochim. Cosmochim. Acta. 37:367-377 (1973)). Formation of chloropyro-morphite [Pb.sub.10 (PO.sub.4).sub.6 Cl.sub.2 ] in soils contaminated through mining activities was reported by Cotter-Howells and Thornton ("Sources and Pathways of Environmental Lead to Children in a Derbyshire Mining Village." Environ, Geochem, Health. 12:127-135 (1991)). Further, they illustrated that the blood Pb levels of children exposed to these contaminated soils was not elevated thus implying that this form of soil Pb is unavailable.